In the drilling and completion industry, the formation of boreholes for the purpose of production or injection of fluid is common The boreholes are used for exploration or extraction of natural resources such as hydrocarbons, oil, gas, water, and alternatively for CO2 sequestration. To increase the production from a borehole, the production zone can be fractured to allow the formation fluids to flow more freely from the formation to the borehole. The fracturing operation includes pumping fluids at high pressure towards the formation to form formation fractures. To retain the fractures in an open condition after fracturing pressure is removed, the fractures must be physically propped open, and therefore the fracturing fluids commonly include solid granular materials, such as sand, generally referred to as proppants. Other components of the fracturing fluids typically include water, gel, or other chemical additives.
To pump the fracturing fluids at the high pressures required for fracturing, a series of mechanical pumps having relatively short strokes and relatively high cycles per minute are employed. Such pumps tend to fatigue rather quickly because of the extreme pressures and the high cycles per minute rate of operation. Further aggravating the system is the fracturing fluid itself, which is either abrasive due to the proppant concentration or corrosive due to an acidic concentration or both The intensifiers include hydraulic cylinders that pump the hydraulic fluid down the borehole by being stroked from another cylinder.
To decrease the strain, pumping systems have been designed to have a longer stroke in order to reduce the number of fatigue and wear pressure cycles for longer service life. Pumping rams which receive working fluid through inlets and discharge working fluid through outlets are connected to power rams which receive fluid to affect the forward pumping strokes of the ram assemblies. Such an intensifier also includes a pre-charged accumulator for driving a pair of twin return rams to affect the return strokes of the ram assemblies.
While the long stroke intensifier is an improvement over pumping systems having shorter strokes, as time, manpower requirements, and mechanical maintenance issues are all variable factors that can significantly influence the cost effectiveness and productivity of a fracturing operation, the art would be receptive to improved apparatus and methods for reducing valve cycles and maintenance issues in a fracturing fluid pump.